Makes resolving ids work correctly in new world

components/mus/ws/test_server_window_delegate.cc

Index: components/mus/ws/test_server_window_delegate.cc
diff --git a/components/mus/ws/test_server_window_delegate.cc b/components/mus/ws/test_server_window_delegate.cc
index b2e7a1e55a032cba4b4128699ba88118581c1438..24677a644f09481adaf9f3d03b3e508e8235bd60 100644
--- a/components/mus/ws/test_server_window_delegate.cc
+++ b/components/mus/ws/test_server_window_delegate.cc
@@ -28,6 +28,13 @@ const ServerWindow* TestServerWindowDelegate::GetRootWindow(
 void TestServerWindowDelegate::ScheduleSurfaceDestruction(
     ServerWindow* window) {}
 
+ServerWindow* TestServerWindowDelegate::FindWindowForSurface(
+    const ServerWindow* ancestor,
+    mojom::SurfaceType surface_type,
+    const ClientWindowId& client_window_id) {
+  return nullptr;
+}
+
 }  // namespace ws
 
 }  // namespace mus